Filter key



FIG. 1 is a perspective view of a filter key in accordance with the present disclosure;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a left side elevation view thereof;

FIG. 5 is a right side elevation view thereof;

FIG. 6 is a front elevation view thereof; and,

FIG. 7 is a rear elevation view thereof.

The portions of the filter key shown in broken lines form no part of the claimed design. 

CLAIM The ornamental design for a filter key, as shown and described. 